1. Field of the Invention
The present invention relates to a high-density mounted device, and more particularly, to a high-density mounted device in which an adhesive sheet is laid between a wiring board and a plurality of semiconductor devices to be mounted thereon.
2. Background Art
FIG. 4 is a cross-sectional view showing a method of mounting a semiconductor device for use with a conventional high-density mounted device. In the drawing, reference numeral 1 designates a wiring board formed from glass epoxy or ceramic; 2 designates a plurality of electrode terminals provided on the primary surface of the wiring board; 3 designates a semiconductor device to be mounted on the wiring board 1; and 4 designates solder balls which are provided on respective un-illustrated electrode terminals of the semiconductor device 3 and arranged in what is commonly called a ball grid array (BGA). Such a solder ball is typified by Snxe2x80x94Pb.
The semiconductor device 3 is mounted on the wiring board 1 by providing the solder balls 4 on the semiconductor device 3 so as to correspond to the respective electrode terminals 2 provided on the wiring board 1, attaching the solder balls 4 to solder paste which as been applied to the wiring board 1 beforehand, and fusing the solder balls 4 and the solder paste, to thereby electrically and mechanically connect the solder balls 4 with the respective electrode terminals 2.
As mentioned above, in the conventional high-density mounted device, a semiconductor device is electrically and mechanically connected to a wiring board through use of solder balls. Since the solder balls 4 are connected with the wiring board 1 by way of point contact, sufficient dissipation of heat developing in the semiconductor package has not been achieved.
In a case where a semiconductor device is a high-frequency circuit, grounding is necessary. Even in such a case, a solder ball is provided on the ground terminal of a semiconductor device, in the same way as mentioned above, and the solder ball is bonded to a ground terminal pattern laid on the wiring board 1, thus resulting in insufficient grounding. As a result, the semiconductor device encounters a problem of an operation circuit being unstable or susceptible to noise.
The present invention has been conceived to solve such a problem and is aimed at providing a high-density mounted device enabling sufficient electrical connection, sufficient heat dissipation, an improvement in grounding, and facilitated mounting of a high density mounted device.
According to one aspect of the present invention, a high-density mounted device comprises a wiring board having a plurality of electrode terminals, and a plurality of semiconductor devices having a plurality of electrode terminals and mounted on the wiring board. An adhesive sheet is interposed between the wiring board and the semiconductor device, and the adhesive sheet includes a sheet-like adhesive base member and a plurality of conductive sections provided at predetermined pitches in the sheet-like adhesive base member. The conductive sections in the adhesive sheet extend from one side of the sheet-like adhesive base member to the other side thereof, and are electrically insulated from each other. The conductive sections enable electrical connection between the electrode terminals of the wiring board and the electrode terminals of the semiconductor device, and constitutes heat conductive channels between the wiring board and the semiconductor device.
According to another aspect of the present invention, in a high-density mounted device, the conductive sections in a adhesive sheet enables electrical connection between the ground terminals of the wiring board and the ground terminals of the semiconductor devices.